Microelectromechanical systems (MEMS), for example, gyroscopes, resonators and accelerometers, utilize micromachining techniques (i.e., lithographic and other precision fabrication techniques) to reduce mechanical components to a scale that is generally comparable to microelectronics. MEMS typically include a mechanical structure fabricated from or on, for example, a silicon substrate using micromachining techniques.
One issue which arises in various MEMS devices is data processing/sensor interaction. One example of this interaction is in devices incorporating a magnetometer and an accelerometer. In order to output correct heading angle data, the tilt of the accelerometer must be compensated. If tilt compensation is not available, the output data is not reliable since unquantified/inconsistent misalignment between the accelerometer and the magnetometer may be present. Similar situations arise in the context of other sensor interactions such as accelerometer-gyroscope interactions and gyroscope-magnetometer interactions.
Accordingly, while different sensors/devices in different chips on a circuit board can be combined to provide up to 10 degrees of sensing freedom (3-axis acceleration, 3-axis angular rate, 3-axis magnetic field, environment pressure), very few of these devices are commercially available since set-up of devices with interaction between heterogeneous sensors is exhausting. The resultant alignment error/discrepancy among sensors hinders end applications. Additionally, circuit board warpage due to stress/temperature can ruin the readouts.
Another approach to providing increased functionality is to use package level integration (system in package or SIP). SIP is derived from the concept of ASIC+MEMS (accelerometer, gyroscope, magnetometer, pressure sensor, . . . ). The advantage of SIP is that multiple MEMS sensors/devices can be integrated. The SIP approach is tenable for limited numbers of sensors, e.g., ASIC+MEMS (accelerometer, gyroscope, magnetometer, . . . ). Incorporation of additional functionality, however, is problematic. For example, because the approach relies upon planar integration, the footprint of the SIP increases rapidly. A large footprint is a particular concern in applications for consumer electronics, such as cellular phones. Vertical integration of the individually packaged sensors is likewise an issue in consumer electronics. Moreover, as the footprint/height of the SIP increases, the potential for alignment errors between sensors also increases.
What is needed is a method of forming wafers such that provides multiple microsensors/microdevices. A wafer that exhibits a small form factor while incorporating multiple microsensors/microdevices is also needed. A wafer incorporating multiple microsensors/microdevices which can be manufactured using proven processes would be further beneficial.